THERMODYNAMICS OF HOMOGENEOUS HYDROGENATION .3. OXIDATIVE ADDITION OF H-2 TO RH(I) COMPLEXES - CORRELATION OF DIHYDRIDES STRUCTURE TO THE THERMODYNAMICS OF THE CATALYZED HOMOGENEOUS HYDROGENATION OF CYCLOHEXANE

Experimental data shows that the stereoselective addition of H//2 to Rh(I) complexes of monodentate, bidentate and terdentate ligands is controlled by electronic and steric factors, pi -acidity of the ligands present in the coordination sphere of the metal ion and chelate ring formation. The migratory insertion of the olefin in the M-H bond seems to be controlled by the dominate entropy factor in the reaction rather than the enthalpy. Sterically related dihydrides of the chelated phosphines show the same catalytic behavior, which is explained in terms of the similarity in the enthalpy and entropy of hydride formation and activation.